The formulation of the various types of lubricating oils vary
significantly depending on their application.
||Anti Wear additive
The main functions / requirements of industrial oils in their
Circulating oils and Turbine oils
A typical system requires bearing lubrication, remove of heat
through circualtion, serve as hydraulic oil, lubricate gears.
Performance requirements are:
A typical system includes a reservoir for the hydraulic fluid, a
pump, transfer channels, and return channels to the reservoir.
These oils provide protection to different types of industrial gears
which are often operated under high contact pressures and / high
speed. There are many combinations of gear types and materials. For
example worm gears interact by predominantly sliding motion whereas
spur gears operate by a combination of rolling and sliding. Therefore,
the requirements for gear oils varied. Lightly loaded spur gears
require an oil with only rust and oxidation inhibiters while heavy
loaded gears require oils with high levels of EP additives. In the
case of worm gears, their action is almost all sliding and not heavily
loaded. Smaller worm gears therefore may be made of bronze for better
sliding wear resistance and may be lubricated by an oil with friction
modifier. In these applications friction modifiers can be more
effective than sulfur-containing EP additives, which might promote
corrosion of bronze worm gears. For large, slow moving gears an
adhesive high viscosity lubricant is required. In applications where
industrial gear oils are used in environmentally sensitive areas such
as forest and near waterways, biodegradable gear oils based on natural
and synthetic esters have been devoloped.
The formulations of compressor oils vary significantly depending on
the type of compressor, reciprocating and rotary gas compressors and
the type of gas being compressed. In reciprocating compressors
lubrication include the crackshaft, bearings, connector rod, wrist
pins, pistons, piston rings, cylinders and valves. Rotary compressors
require lubrication of bearings, seals and shafts. High pressure
reciprocating compressors require lubricants stable for high
temperatures, usually synthetic esters. Rotary vane compressors
require lubricants that minimize vane wear, usually synthetic PAO's
due to their good thermal stability and lower cost relative to
synthetic esters. Compressor manufacturers generally designate the
compressor oil formulations that are suitable for their equipment.
The main functions of a cutting oil are to lubricate or reduce
friction between the tool and the workpiece, and to act as a coolant
by rapidly removing heat generated at the tool-workpiece interface.
Soluble cutting oils are mixed with water in proportions of 3 to10%.
They are used where rapid heat removal is a major requirement. Usually
formulated with emulsifiers, rust inhibitors, and EP additives.
Insoluble cutting oils are used in operations involving tough cutting
such as tapping, threading, and broaching. Lubricity and anti-weld
characteristics are important characteristics of this cutting oil.
These oils are formulated to lubricate saw chains, and should provide
the following benefits:
An unbroken film of lubricant between chain links and bars.
Anti-wear characteristics to prevent chain and bar wear.
Prevent corrosion of the chain.
The automobile industry is the major user of lubricants. Engine
designs have been continually improved to reduce weight, increase fuel
economy, increase power output, and at the same time meet
environmental emission guidelines. Research is ongoing to formulate
lubricants to meet the demands of the redesigned engines. In general,
a lubricant must perform nine functions for the efficient operation of
1. Permit Easy Starting
An engine oil must be thin enough when first starting the engine to
allow for sufficient cranking speed. The oil must then be able to flow
immediately to lubricate vital engine components. Most of the engine
wear occurs at start-up before the oil can reach all the engine parts.
As the engine is heated, the oil must not become too thin and be
unable to provide adequate engine lubrication. The viscosity of the
oil is the measure of this resistance to flow.
The effect of temperature on viscosity varies widely with different
types of oil. The standard used to measure the amount of viscosity
change with temperature is the Viscosity Index (V.I). An oil with a
high viscosity index shows less change in viscosity over a wider
temperature range. Refer to the Glossary of Terms, and the Additive
section of this site for more information. A "multi-grade" oil has a
high viscosity index.
Synthetic oils have the best low temperature flow characteristics, and
are worth the extra cost in northern climates during the winter
2. Lubricate and Prevent Wear
The engine is now started, and the oil is being circulated by the oil
pump to the engine parts. The oil must now prevent the metal-to-metal
contact that will result in wear to the moving parts.
Full-film lubrication occurs when the moving surfaces are continuously
separated by a film of oil. The viscosity of the oil must remain high
enough to prevent metal-to-metal contact. Wear will only occur if the
surface is scratched by particles thicker then the oil film.
Crankshaft bearings, connecting rods, camshaft, and piston pins
normally operate with full-film lubrication.
In some conditions, it is impossible to maintain a continuous oil film
between the moving parts. Intermittent metal-to-metal contact occurs
because of high spots on sliding surfaces, during engine starting, and
in new or rebuilt engines. Lubrication under these conditions is
referred to as boundary lubrication. This lubrication is accomplished
by the additive package in the oil. Refer to the Glossary of Terms for
further information on boundary lubrication.
3. Reduce Friction
Under full-film lubrication conditions, the film of oil prevents
metal-to-metal contact. The viscosity of the oil should be high enough
to maintain the film. A delicate balance must be maintained. If the
viscosity is higher then required, the engine must overcome the excess
It is important to note that the viscosity of the oil changes as it
becomes contaminated. Dirt, oxidation and sludge will increase the
viscosity of the oil while fuel dilution will reduce the viscosity.
This is the reason why the oil must be changed as per the schedule in
the owners manual.
4. Protect Against Rust and Corrosion
Under perfect conditions, fuel burns to form carbon dioxide and water.
For each gallon of fuel burned, a gallon or more of water is produced.
Most of this water should escape as a vapor out of the exhaust, but
some does condense on the cylinder walls. Also, water passes by the
piston rings and becomes trapped in the crankcase. This is more of a
problem in cold weather before the engine is warm.
In addition to water, other corrosive combustion gases also get past
the rings, and are dissolved in the crankcase oil. Add to this the
acids formed by the normal oxidation of oil, and the potential for
rust and corrosive engine deposits become significant.
Corrosion inhibitors are part of the additive package to protect
non-ferrous metals by coating them, and forming a barrier between the
parts and the acids. Also, rust inhibitors are added to the oil to
protect iron/steel surfaces from oxygen attack by forming a protective
5. Keep Engine Parts Clean
For a variety of reasons, a gasoline or diesel engine does not burn
all the fuel completely. Some of the partially burned gasoline or
diesel fuel undergoes complex chemical changes during combustion, and
under some conditions forms soot or carbon. Most of the partially
burned fuel escapes in the form of soot through the exhaust, but part
escapes past the rings into the crankcase. This combines with water to
form sludge, and varnish deposits on engine parts. Sludge buildup may
clog oil passages which reduces oil flow. Varnish buildup interferes
with the proper clearances, restricts oil circulation, and causes
vital engine parts to stick and malfunction.
Straight mineral oils have a very limited ability to keep these
contaminants from forming sludge within the engine. Detergents are
part of the additive package to clean-up existing deposits in the
engine, as well as disperse insoluble matter into the oil. Dispersants
are also part of the additive package. Both detergents and dispersants
attach themselves to contaminated particles and hold them in
suspension. The suspended particles are so finely divided that they
can pass harmlessly between the mating surfaces, and through the oil
filter. This contamination is removed when the oil is changed. Another
good reason for your scheduled oil change!
6. Minimize Combustion Chamber Deposits
Some oil must reach the area of the top of the piston ring in order to
lubricate the rings and the cylinder walls. It is important that the
oil prevent excessive combustion deposits. Combustion deposits act as
a heat barrier and as a result pistons, rings, spark plugs, and valves
are not properly cooled. We all know about carbon fouled spark plugs.
The motor oil must accomplish two things in preventing excessive
The oil must keep the rings free so as to reduce the amount of oil
reaching the combustion chamber.
The portion of the oil reaching the combustion chamber must burn as
clean as possible.
7. Cool Engine Parts
The cooling system performs about 60% of the cooling job of the
engine. It cools the upper part of the engine including the cylinder
heads, cylinder walls, and valves. The crankshaft, the main and
connecting rod bearings, the timing gears, the pistons and other
components in the lower engine are cooled as the oil flows around the
What is critical is the continuous circulation of large quantities of
oil. If oil passages are allowed to become clogged, the flow is
restricted, and the parts are not cooled properly. Another good reason
to change your oil on a regular basis, and check the oil level!
8. Seal Combustion Pressures
The surfaces of the piston rings, ring grooves, and cylinder walls are
not completely smooth. This would become evident under a microscope as
small hills and valleys. For this reason, the rings can never prevent
high combustion and compression pressures from escaping into the low
pressure area of the crankcase. This would result in a reduction of
engine power and efficiency. Motor oil fills in the hills and valleys
and greatly improves the seal. Because the oil film is only about
0.025 mm thick, it cannot compensate for excessive wear of the rings,
ring grooves, or cylinder walls. In a new or rebuilt engine, oil
consumption will be relatively high until these surfaces have been
smoothed out enough to allow the oil to form a good seal.
9. Engine Oil Must be Non-Foaming
Because of the rapidly moving parts in an engine, oil is constantly
being mixed with air. This produces foam which is a lot of air bubbles
which may or may not readily collapse. These air bubbles normally rise
to the surface and break, but water and other contaminants slow this
Foam is not a good conductor of heat, and will impair the cooling of
the engine parts. Also, foam does not have the ability to carry much
of a load which would result in excessive engine wear.
Foam depressant additives are used in the manufacture of automotive
lubricants, to reduce the amount of foaming.
Detergents are used to perform two key functions. One is to
neutralize the acidity byproducts of lubricant oxidation and thermal
decomposition and the other is to keep contaminants as sludge of
oxidized oil soluble. The total base number (TBN) of the detergent
reflects its ability to neutralize acids.
Dispersants control contamination from low temperature
operation. Both detergents and dispersants attach themselves to
contaminant particles, and hold them in suspension. The suspended
particles are so finely divided that they pass harmlessly between
mating surfaces and through oil filters. The contamination is removed
from the engine when the oil is changed.
Oxidation Inhibitors reduce oxygen attack on the lubricating
Corrosion Inhibitors protect non-ferrous metals by coating them
and forming a barrier between parts and their environment.
Rust Inhibitors protect iron/steel from oxygen attack, by
forming a protection screen over the surface of the metals.
Friction modifiers reduce friction by physical adsorption of
polar materials on metal surfaces (fatty acids and esters,
Anti-Wear agents form a protective layer by chemical reaction
with the metal surface (normally a metal soap).
Extreme Pressure additive also known as antiseize additive,
antiscuffing additive, form a protective layer by chemical reaction
with the metal surface, increasing the load at which scuffing or
Foam Depressants controls the tendency for fouming. Detergent
and dispersant additives can facilitate aeration of an oil which
results in foaming. This can reduce the lubricating ability of the
oil, and interfere with the pumping of the oil.
Viscosity Index (VI) Improvers control the viscosity of
multi-grade oils. They are long-chain polymers that function by
uncoiling or dissociating at elevated temperatures, increasing the
oil's resistance to flow. At low
temperatures, they are "tight-balls" which do not significantly
increase the oils resistance to flow.
Pour Point Depressants give an oil better low temperature